Belt sanding and polishing machines



Jan. 23, 1968 w. c. KEYES BELT SANDING AND POLISHING MACHINES 5 Sheets-Sheet 1 Filed Aug. 12, 1964 IIIIYPI: I I. 1.511;!

INVENTOR WILLIAM C. KEYES ATTORNEY Jan. 23, 1968 w. c. KEYES BELT SANDING AND POLISHING MACHINES 5 Sheets-Sheet 2 Filed Aug 12, 1964 m QR INVENTOR.

'W \LLIAM C. KEYES ATTORNEY Jan. 23, 1968 w. c. KEYES 3,364,626

BELT SANDING AND POLISHING MACHINES Filed Aug. 12, 1964 5 Sheets-Sheet 3 INVENTOR. WILLIAM C. KEYES ATTORNEY Jan. 23, 1968 w. c. KEYES 3,

BELT SANDING AND POLISHING MACHINES Filed Aug. 12, 1964 5 heets-she t 4 I n g I g as if LI 8 $I :a N 2;

2 l a o l I la i E 1 5 E E w E I E E g INVENTOR. g

WILLIAM C. KEYES BY y ATTORNEY Jan. 23, 1968 w. c. KEYES BELT SANDING AND POLISHING MACHINES 5 Sheets-Sheet Filed Aug. 12, 1964 INVENTOR.

WILLIAM C. KEYES ATTORNEY fwd United States Patent 3,364,626 BELT SANDING AND POLISHING MACHINES William C. Keyes, North Tonawanda, N.Y., assignor to The Carborundnm Company, Niagara Falls, N.Y., a corporation of Delaware Filed Aug. 12, 1964, Ser. No. 389,090 14 Claims. (Cl. 51-138) This invention relates to belt sanding and polishing machines and, more particularly, to pressure pads for sanding and polishing machines.

Certain species of wood, such as mahogany and walnut, have a pleasing surface appearance, but they are relatively expensive in comparison with more common species, such as pine and fir. Accordingly, it is a common practice in the furniture industry to apply a thin sheet of veneer of a fine grade wood to a core made of a less expensive wood, so that the veneered panel appears to be a solid piece of wood of the more expensive species. Veneered panels are commonly used in table tops, drawer fronts and other flat surfaces. Veneer may also be applied to sheets of plywood for furniture, or for door or wall panels.

Initially, the veneer sheet, which may be about th of an inch thick, has a relatively rough surface. After the sheet of veneer is adhesively bonded to a core, the veneered panel is rough sanded to remove surface irregularities and unevenness. Rough sanding removes about onehalf of the thickness of the veneered sheet.

The veneered panels are then polished to provide a smooth, even surface. The polishing operation removes only a few thousandths of an inch of veneer. An endless belt type sanding and polishing machine is preferred for the polishing operation, since it produces a superior finish on the surface of the veneer. To obtain the optimum surface finish the belt should travel across the panel in the same direction as the grain of the wood in the veneer. Since veneered panels usually have the wood grain of the veneer parallel to the longest dimension of the panel, the length as used herein refers to the direction parallel to that of the wood grain. The belt pulleys of the machine are spaced wider apart than the length of a panel and an endless abrasive belt is stretched between the pulleys and runs across the veneered surface of the panel. It is necessary to press the abrasive belt against the surface of the panel to assure uniform polishing, and accordingly, a pad is usually mounted on the machine for urging the belt against the surface of the veneered panel with a uniform pressure. The pad may be in the form of a fiber or felt mat which is mounted on a rigid support. The pad is pressed against the abrasive belt by a pneumatic cylinder or other means.

Since the abrasive belt has a run which is longer than the length of the veneered panels, the belt tends to drag across the ends of the panels when the pad is pressed against the belt. The veneer sheets are extremely thin and the concentrated abrasive forces along the ends of the veneered panel as the belt passes over the end of the panel, often cause the veneer to be sanded through, so that the core is exposed.

In view of these defects in conventional sanding and polishing machines, it is an object of the present invention to improve such sanding and polishing machines of the character described.

It is a further object of this invention to provide for sanding and polishing veneered panels, without sanding through the veneer along the ends of the panels.

It is a still further object of this invention to provide a sanding and polishing machine in which the effective pad length is adjustable for panels of various widths.

These objects are accomplished in accordance with a preferred embodiment of the invention, by asanding "ice and polishing machine having an endless abrasive belt stretched between pulleys which are mounted on a frame. The abrasive belt extends across a work supporting surface. A back-up belt is stretched between pulleys which are mounted on the frame between the pulleys of the abrasive belt, thereby positioning the back-up belt in substantially the same plane as the abrasive belt, but inside the abrasive belt. The lower run of the back-up belt extends along and adjacent to the lower run of the abrasive belt which is adjacent to the work supporting surface. A caul assembly is supported on the frame and extends between the runs of the back-up belt. A pad is mounted on the undersurface of the caul assembly and the caul assembly is movable vertically for selectively pressing the pad against the back-up belt, which in turn presses the ibrasive belt against a workpiece on the supporting surace.

The caul assembly has tracks suspended along opposite longitudinal edges of a flat plate and the pad has logitudinal flanges which are supported on the tracks. The flanges may be formed, for example, by a flexible metal sheet which extends laterally between the tracks and along the lengths of the caul plate, with the pad being secured to the bottom surface of the sheet. The pad is sufficiently thick to extend below the level of the tracks. A pair of endless composite belts extend separately along each of the opposite sides of the caul plate and each belt of the pair on the same side of the caul plate is in substantially the same plane. The bottom run of each of the pairs of belts extends under the flexible sheet to which the pad is secured. Each of the endless belts is a composite belt formed of a length of roller chain and a length of tape joined end-to-end to form a single endless belt. The pairs of composite belts are adjusted longitudinally, so that the roller chain portions of each composite belt on one side of the caul plate are in substantial alignment with the roller chain portions of the corresponding composite belt on the other side of the caul plate.

Portions of each composite belt extend between the track and the flange from which the pad is suspended, and since the roller chains are considerably thicker than the tape, they raise the pad relative to the tracks. Consequently, the portion of the pad supported on the roller chain portions of the composite belt does not engage the back-up belt when the caul plate is lowered, while the portion of the pad supported on the tapes is pressed against the back-up belt to apply sanding and polishing pressure. One belt on each side of the caul plate controls the elevation of one end of the pad and the other belt on each side of the caul plate controls the elevation of the opposite end of the pad. By adjusting the positions of the roller chain portions supporting the pad, the length of the intermediate portion of the pad which is supported on the tapes may be adjusted to correspond to the width of a workpiece on the supporting surface.

To provide pressure for urging the pad against the belts, an air bag is inflated between the pad supporting sheet and the caul plate. The inflated air bag displaces the sheet away from the caul plate, but at the ends of the caul plate, the sheet is supported on sprocket chains which maintain a separation between the back-up belt and the pad, although the air bag is inflated. The intermediate portion of the sheet is supported on the tapes, and accordingly, that portion of the pad is pressed against the back-up belt by the pressure of the air in the bag.

The pulleys on which the abrasive belt and back-up belt are mounted are spaced sufiiciently above the pad for the portion of each belt to extend in upwardly sloping relation with the work supporting surface between the marginal edge of the workpiece and the pulley. Since the length of the lowered portion of the pad may be adjusted by means of the composite belts, the effective sanding and polishing length may be adjusted to correspond to the length of the veneered panels and thereby avoid sanding through the veneer along the marginal edges.

This preferred embodiment of the invention is illustrated in the accompanying drawings in which:

FIG. 1 is a top plan view of the sanding and polishing machine according to this invention;

FIG. 2 is a front elevational view of the machine;

FIG. 3 is a cross sectional view of the machine, taken along the line 33 in FIG. 2, and is partially schematic;

FIG. 4 is a front elevational view, partially schematic, of the caul assembly;

FIG. 5 is a top plan view of the caul assembly;

FIG. 6 is a cross sectional view of the caul assembly, taken along the line 6-6 in FIG. 4; and

FIG. 7 is an enlarged detail view of the pad suspension.

Referring to FIGS. 1 and 2, the sanding and polishing machine according to this invention has an elongated horizontal frame 2, which is supported at opposite ends on upright pedestals 4 and 6. Back-up puleys 8 and it) are journaled in bearings on the frame 2 and belt pulleys 12 and 14 are also journaled for rotation on the frame 2. A back-up belt 16 extends over the back-up pulleys 8 and 19, and an abrasive belt 18 extends over the pulleys 12 and 14.

A conveyor frame 20 extends transversely under the frame 2 and is supported by screw jacks 22, which are mounted on the pedestals 4 and 6. The conveyor frame 20 is raised and lowered selectively by a motor 24 in the pedestal 4 and which drives the jacks 22. The belt pulleys and 14 are driven by a motor 26 in the pedestal 6. The pulleys 10 and 14 turn in the same direction and the belt is driven at approximately one half of the linear speed of the abrasive belt. A caul assembly 28 which is mounted on the frame 2 urge the lower runs of the belts 16 and 18 against a workpiece on the conveyor frame 20.

The conveyor frame 20 has rollers 30 mounted for rotation at opposite ends of the frame, and an endless conveyor belt 32 extends over the rollers 30. A base plate 34 (FIG. 3) under the upper run of the conveyor 32 provides a flat rigid support for the flexible conveyor and a motor (not shown) advances the conveyor 32 at a uniform speed. The belts 16 and 18 and the caul assembly 28 are enclosed in a housing 36 for collecting the dust generated while the belt 18 is sanding and polishing a workpiece. The dust laden air is drawn out of the housing 36 through outlets 38 at opposite ends of the housing 36 by conventional dust removal equipment.

As workpieces on the conveyor belt 32 advance under the housing 36, the leading edge of each workpiece engages a stock feed switch 40 (FIGS. 2 and 3) which controls the position of the caul assembly 28. The switch 40 is mounted on a rigidly supported strip 41 which extends across the front of the housing 36 and the switch 46 may be positioned at any desired location along the length of the strip 41. Since the switch 48 is spaced from the caul assembly and the belts 16 and 18, there must be a sufficient delay to allow the workpiece to move under the belts 16 and 18 before the caul assembly 28 is lowered. The delay mechanism is of conventional construction and is responsive to the speed of the conveyor 32. Vertical movement of the caul assembly 28 is accomplished by a hydraulic caul cylinder 42 (FIG. 1) which is mounted on the frame 2. A bar 44 extends along the frame 2 and levers 46 are secured to each opposite end of the bar 44. Each of the levers 46 is journaled for swinging movement in bearings 47 (FIG. 3) on the frame 2. The outer end of each lever 46 is connected to a bracket 48 extending upwardly from the caul assembly 28.

When fluid is directed into the cylinder 42 on one side of the piston, the piston moves downwardly, thereby moving the bar 44 downwardly. Since the bar 44 is connected at opposite ends to the levers 46, the levers swing about their respective bearings 47, and the opposite end of each lever 46 swings upwardly to lift the caul assembly 28. Conversely, when hydraulic fluid is pumped under pressure into the caul cylinder 42 on the opposite side of the piston, the piston is retracted into the cylinder, thereby lowering the caul assembly 28 relative to the frame 2.

A work guide fence 50 (FIG. 1) is secured to the conveyor frame 20 and extends lengthwise over the conveyor belt 32. A similar work guide fence 52 may also be provided on the conveyor frame 20 on the opposite side of the caul assembly for maintaining workpieces within prescribed paths under the caul assembly. A plurality of rollers 53 are mounted along the front and back of the housing 36 for holding workpieces securely against the conveyor 32. The position of the rollers is adjustable for holding workpieces securely against the conveyor 32.

It is important to maintain the caul assembly 28 parallel to the plane of the conveyor 32, and for this purpose a linkage 54, as shown in FIGS. 1 and 2, adjusts the vertical position of the inner end of one of the levers 46 relative to the 'bar 44. When the point of connection of the lever 46 with the bar 44 is lowered, the opposite end of the bar 44 is raised, and accordingly the caul assembly 28 may be tilted about its transverse axis until the caul assembly is parallel to the conveyor 32. A wheel 56 on the front of the housing 36 operates the linkage for raising and lowering the opposite ends of the caul assembly relative to each other.

It is also necessary to adjust the force of the caul assembly on the belts and the workpiece. A linkage 58, as shown in FIG. 1, between the caul cylinder and the frame 2 permits the distance between the cylinder and the bar 44 to be adjusted and thereby allows an adjustment of the grind pressure provided by the caul assembly. A wheel 68 on the housing 36 is provided for adjustment of the linkage 58.

As shown schematically in FIG. 3, the endless conveyor belt 32 extends under the caul assembly 28 and is supported by the plate 34. The abrasive belt 18 and the backup belt 16 have their lower runs extending between the assembly 28 and the conveyor 32. The stock feed limit switch 40 which controls the position of the caul assembly 28, is mounted on the strip 41 in position to be actuated by a workpiece moving on the conveyor 32 toward the caul assembly 28.

Workpieces, which may be in the form of panels having thin veneer facings, are advanced on the conveyor belt 32 under the caul assembly 28. Referring to FIGS. 3 to 7, the caul assembly 28 includes a suitable support member such as an elongated channel member 62. A caul plate 64 extends along the channel member 62 and is secured thereto by welding or other suitable means. Thin rigid frames 66 and 68 extend along opposite sides of the channel member 62, and are secured by welding or other suitable means to the opposite edges of the caul plate 64. The lower edgesof the frames 66 and 68 have inwardly turned flanges 70 and 72, respectively. A thin flexible, preferably metallic, sheet 74 is mounted between the frames 66 and 68 and extends substantially the full width and length of the caul plate '64. A pad 76 is secured to the sheet 74 and extends along substantially the entire length of the sheet. However, the pad 76 is not as wide as the sheet 74 and is of a thickness to be located between the inner edges of the flanges 70 and 72.

The pad 76 is slightly compressible and may be formed of a fibrous material or an elastomeric material. To protect the pad 76 from excessive wear and to urge it against the caul plate 64, a canvas 78 is stretched under the pad 76. The canvas 78 is preferably a fabric impregnated with a lubricant, such as graphite. The canvas 78 extends along the length of the pad 76 and is stretched over rollers 80 (FIG. 4) which are mounted on shafts 81 on opposite ends of the channel member 62. The ends of the canvas 78 are secured in clamps 82, shown in FIGS. 4, 5 and 6. At each opposite end of the channel member 62, a support bracket 84 is fastened to the channel member, and

a stud 86 extends through the bracket 84 and is threaded through an internally threaded hole in the clamp 82. The stud 86 is journaled in a hole in the bracket 84, and a wing nut 88 is secured on the stud 86. Turning the nut 88 draws the canvas taut over the rollers 80.

As shown in FIG. 4, the rollers 80 are above the flanges 70 and 72 and to allow adjustment of the slope of the canvas between the pad and the roller, a positioning plate 90 extends between the roller 80 and the caul plate 64 at each opposite end of the caul plate 64. Each positioning plate 90 has an internally threaded hole therein through which a screw 92 is threaded. A hand wheel 94 is secured to the screw 92, which also extends through the bracket 84 and is journaled therein. By turning the hand wheel 94, the positioning plate 90 may be displaced relative to the roller 80.

Between the flexible sheet 74 and the caul plate 64 is an inflatable bag 96. As shown in FIG. 6, the bag 96 preferably has separate cells 98 which extend longitudinally of the caul plate 64. Suitable means are provided for supplying air at a regulated pressure to each of the cells 98. in FIG. 3, the air bag 96 is shown in the collapsed condition, and the pad 76 is separated from the back-up belt 16, while in FIG. 6, the air bag 96 is shown as inflated, so that the pad 76 is pressed against the back-up belt 16 for sandin and polishing a workpiece W on the conveyor 32.

It will be apparent that when the air bag 96 is inflated, the pad 76 is pressed against the back-up belt 16 along the entire length of the caul plate 64. This is undesirable if the veneered workpiece W is not as wide as the caul plate is long, sirice the pad 76 presses against the abrasive belt 18 beyond the edge of the workpiece and causes the thin veneer on the workpiece to be sanded through. Accordingly, it is necessary to raise the opposite ends of the pad 76 to adjust the effective length of the pad to correspond to the width of the workpiece.

Adjustment of the effective length of the pad 76 is accomplished by composite belts which extend between the flexible sheet 74 and the flanges 70 and 72. Each composite belt is formed of a length of conventional roller chain 100 and a length of thin flexible tape 102, which is preferably metallic. The opposite ends of each roller chain 109 are connected to the opposite ends of a tape 102 to form an endless composite belt having a roller chain portion and a tape portion. A pair of endless composite belts are mounted on each opposite side of the caul plate 64 at each lateral edge of the plate.

As shown in FIG. 4, pairs of endless composite belts are mounted in substantially the same manner at the front and rear of the caul assembly. One composite belt of each pair has a length of roller chain 100 which extends over a sprocket gear 104. The sprocket gears 104 are keyed on the opposite ends of the shaft 81 which also carries the roller 80, but the roller is free to rotate relative to the shaft 81. Each roller chain 100 extends under the left end of the caul plate 64 as viewed in FIG. 4, where the end of each roller chain is fastened to a tape 102, by welding or other suitable means. The tapes 162 extend along the caul plate 64, between the sheet 74 and the flange 70 (FIG. 6). At the right end of the channel member 62 (FIG. 4), the tapes 102 extend over a shoe 106. The end of each tape 102 is fastened to a turnbuckle S, and the opposite end of the respective turnbuckles are fastened to the corresponding roller chain 100. The turnbuckles 103 are used for adjusting the tension in the endless composite belts.

The other endless composite belt of each pair is mounted on the caul assembly in substantially the same vertical longitudinal plane as the first endless belts, and each belt includes a roller chain 110 which extends along the caul plate 64 and over sprocket gears 112 which are keyed on opposite ends of the other shaft 81. The end of each roller chain 110 is secured to a tape 114 which extends along the caul plate between the tape 162 and the sheet 74. As shown in FIG. 6, the tapes 114 are superimposed on the tapes 102, and both of the tapes 102 and 114 extend between the sheet 74 and the flange 70. The tape 114 is looped over a peg 116 on the end of the caul plate 64, as shown in FIGS. 4 and 5. One end of the tape 114 is fastened to a turnbuckle 118 and the opposite end is secured to the chain 110. The turnbuckle 118 permits adjustment of the tension in the endless belt formed by the chain and the tape 114.

The roller chain 106 at the rear of the caul assembly is also used for adjusting the longitudinal positions of the junctions between the chains 100 and the tapes 102 at the front and rear of the caul plate 64. For this purpose, the chain 100 at the rear of the caul plate extends from the sprocket wheel 104 upwardly, as shown in FIG. 4, and over a sprocket wheel 120. As shown in FIGS. 4 and 5, a shaft 122 is supported for rotation in bearings 124 which are mounted on the channel member 62. The sprocket gear is secured on one end of the shaft 122 and a hand wheel 126 is secured on the opposite end of the shaft. The roller chain 100 extends over the sprocket gear 120 and over an idler sprocket gear 128 which is mounted for rotation on the channel member 62. By turning the hand wheel 126, the roller chain 100 may be displaced longitudinally. Since both the sprocket gears 104 are keyed to the shaft 81, movement of the roller chain 100 by the hand wheel 126 also rotates the sprocket gear 104 at the front of the caul plate 62 to displace the front roller chain 100 longitudinally a distance corresponding the displacement of the chain 100 at the rear of the caul plate.

The composite belts formed of the roller chains 116 and the tapes 114 may also be displaced longitudinally. A shaft is supported for rotation in bearings 152 which are mounted on the channel member 62, as shown in FIGS. 3, 4 and 5. A sprocket gear 154 is keyed on one end of the shaft 150 and a hand wheel 156 is keyed on the opposite end of the shaft 150. The shaft 81 on the right hand end of the caul assembly, when viewed as in FIG. 5, extends outwardly from the sprocket gear 112 and another sprocket gear 158 is keyed on the shaft 81. The sprocket gear 158 is in substantial alignment with the sprocket gear 154 and a roller chain 160 extends over the sprocket gears 154 and 158, so that by turning the hand wheel 156, the shaft 81 may be turned to cause longitudinal movement of the roller chains 110.

The junctions between the roller chains 100 and their respective tapes 102 are in substantial alignment on opposite sides of the caul plate 64. Furthermore, at the 0pposite end of the caul assembly the junctions between the roller chains 110 and their respective tapes 114 are also in substantial alignment with each other on opposite sides of the caul plate 64.

As shown in FIG. 4, chain portions 110 of the composite belts at the right end of the caul assembly raise the end of the flexible sheet 74 away from their respective flanges 70 and 72. Similarly, the chain portions 100 of the composite belts at the left end of the caul assembly raise the opposite end of the flexible sheet 74 away from their respective flanges 70 and 72. The portion of the sheet 74 between the ends of the chains 100 and 110 is supported on the tapes 102 and 114. When either of the hand wheels 126 or 156 is turned, the corresponding chains 100 or 110 are displaced longitudinally to shift the position of the junctions of the tapes and chains under the sheet 74. Although the graphite canvas 75 draws the pad 76 and the sheet 74 against the caul plate 64, the inflated bag 96 presses the sheet 74 and the pad 76 toward the back-up belt 16. At the ends of the air bag, however, the roller chains raise the pad and the sheet away from the back-up belt. Consequently, as shown in FIG. 7, the pad is drawn against the caul plate 64 by the canvas 78. The effective length of the pad can be changed merely by adjusting the longitudinal position of chain and tape junctions.

As shown in FIG. 4. a workpiece W having a length less than the length of the pad 76 passes under the caul assembly 28 and is sanded or polished by the abrasive belt 18. The positions of the junctions between the tapes and the roller chains of the composite belts determine the break-away point at which the pad separates from the backup belt 16. A pair of pointers 162 (FIG. 6) extend upward on the outside of the housing 36 to indicate the position of the junctions between the tapes and roller chains, but the break-away points are spaced toward the middle of the conveyor 32 a short distance. The distance between the junctions and the break-away point depends primarily upon the air pressure in the bag 96.

The positions of the break-away points may be adjusted by the hand wheels 126 and 156 (FIG. 4). When the caul assembly 28 has been raised by the caul cylinder 42 (FIG. 1), and the bag 96 has been deflated, either hand wheel 126 or 156 may be turned to displace the respective roller chains and thereby to adjust the positions of the break-away points. By turning one or both of the hand wheels, the break-away points of the pad 76 may be adjusted to correspond to the length of the workpiece W. The Work guide fence 50, as shown in FIGS. 1 and 2, maintains the edge of the workpiece in alignment with the break-away points as the workpiece moves under the caul assembly 28 on the conveyor 32.

The back-up belt 16 may be a conventional endless belt of a uniform thickness, but the belt also may have means for concentrating pressure on the abrasive belt 18. An example of a means for concentrating the grinding pres sure may be a plurality of shoes which are applied to the outer surface of the back-up belt 16 at uniformly spaced intervals along the length of the belt. These shoes bear against the inner surface of the abrasive belt 18. Another load concentrating means may be a plurality of diagonal stripes which are secured to the outer surface of the backup belt 16, for example, by an adhesive. The diagonal stripes may be arranged alternatively at right angles, or may be in the form of chevrons to concentrate the grinding pressure on the abrasive belt, without causing the belt to wear excessively. Although the back-up belt 16 contributes to the efficient removal of stock from workpieces and reduces the heat generated by the friction of the abrasive belt, the machine of this invention may be operated without a back-up belt. When a back-up belt is not used, the caul assembly presses the pad against the abrasive belt.

In operation, the air bag 96 is initially deflated and the caul assembly 28 is raised relative to the belts 16 and 18. A workpiece W is placed under the caul assembly 28 and the hand wheels 126 and 156 are used to adjust the positions of the roller chains and tapes until their junctions are spaced a specified distance away from the lateral edges of the workpiece W. The work guide fences 50 and 52 are adjusted to align the workpiece with the break-away points of the pad 76. The distance between each pointer 162 and the corresponding break-away point of the pad 76 is known, since the distance changes in relation to the air pressure in the bag 96. For example, with an air pressure in the bag 96 of 4 psi, the break-away point is approximately two inches on the inboard side of each pointer 162. After the positions of the composite belts have been adjusted, air is supplied at the prescribed pressure to inflate the bag 96 and the caul assembly 28 is lowered by means of the caul cylinder 42. If the caul assembly should be tilted, it may be leveled by means of the hand wheel 56.

The conveyor frame 20 is raised by the jack screws 22 until the workpiece W is engaged by the abrasive belt 18. The pressure of the abrasive belt 18 on the workpiece should be light enough to allow the abrasive belt 18 to be moved longitudinally by hand over the workpiece. The stock feed switch 40 is positioned on the bar 41 to engage the workpieces as they move toward the caul assembly. The machine is then ready for production.

The motor 26 is energized to rotate the pulleys and 14 and drive the back-up belt 16 and the abrasive belt 18, respectively. When the belts 16 and 18 begin to move,

the caul assembly 23 is raised relative to the belts, so that they move freely between the caul assembly and the conveyor 32. As the workpiece moves toward the caul assembly 28 on the conveyor 32, it is guided by the work guides 50 and 52 and when the leading edge of the workpiece engages the stock feed switch 40, a control which operates in timed relation with the conveyor drive, operates a valve for supplying fluid to the caul cylinder 42 at the moment the workpiece has moved under the abrasive belt 18. The caul cylinder then lowers the caul assembly 28 to press the belts 16 and 18 against the workpiece. Workpieces of the same length are fed continuously on the conveyor 32 and as the trailing edge of the last piece moves under the feed switch 4t), the caul cylinder raises the caul away from the belts 16 and 18, after a time delay to allow the workpiece to move under the belts 16 and 18.

A particular advantage of this invention is that the effective length of the pad 76 may be adjusted readily to correspond to the length of a workpiece. Furthermore, the use of an air bag 96 between the caul plate 64 and the back-up belt 16 allows the belt to conform to slight irregularities in the surface of the workpiece. The abrasive belt 18 often is used primarily for polishing the workpiece rather than for removing substantial amounts of material from the surface of the workpiece. Therefore, if there are slight depressions, for example, in the surface of the workpiece, the belt 18 will follow the depression and evenly polish the entire surface. The bag 96 readily adapts itself to the contour of the workpiece. Since the bag 96 extends along the length of the caul assembly 18 between the junctions of the composite belts, the sanding and polishing pressure is uniformly distributed throughout the entire effective length of the abrasive belt.

While this invention has been illustrated and described in one embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.

I claim:

1. A sanding and polishing machine comprising a frame, a pair of pulleys mounted for rotation on the frame, an abrasive belt extending over the pulleys, a work supporting table on said frame between said pulleys, a pad on the side of the abrasive belt opposite the table, a caul assembly mounted on the frame, said caul assembly having a pair of flanges extending along and overlapping the opposite sides of the pad, an endless belt mounted on each opposite side of the caul assembly, each of said endless belts having a run extending between said pad and said overlapping flange, said endless belts each having a length which is relatively thick and a length which is relatively thin, and means for urging the pad against the abrasive belt, whereby the thick lengths of the endless belts displace the pad away from the flanges and only the undisplaced portion of the pad urges the abrasive belt against the workpiece.

2. A sanding and polishing machine comprising a frame, a pair of pulleys mounted for rotation on the frame, an abrasive belt extending over the pulleys, a work supporting table on said frame between said pulleys, a pad on the side of the abrasive belt opposite the table, a caul assembly mounted on the frame, said caul assembly having flanges extending along opposite sides thereof, a flexible sheet extending between and overlapping said flanges, said pad being secured to said sheet, said caul assembly having a backing plate extending along the sheet, an inflatable bag between the sheet and the plate, means for inflating the bag, an endless belt mounted on each opposite side of the plate, each of said endless belts having a run extending between the flange and the overlapping sheet, said endless belts each having a length which is relatively thick and a length which is relatively thin, and means for urging the pad against the abrasive belt, whereby the thick lengths of the endless belts displace the pad away from the abrasive belt and only the undisplaced portion of the pad urges the abrasive belt against the workpiece.

3. A sanding and polishing machine comprising a frame, a pair of pulleys mounted for rotation on the frame, an abrasive belt extending over the pulleys, a work supporting table on said frame between said pulleys, a pad on the side of the abrasive belt opposite the table, a caul assembly mounted on the frame, said caul assembly having a pair of flanges extending along and overlapping the opposite sides of the pad, an endless belt mounted on each opposite side of the caul assembly, each of said endless belts having a run extending between said pad and said overlapping flanges, said endless belts each having means thereon for displacing the pad away from said flanges, a flexible strip extending along the pad adjacent the abrasive belt, means for securing the strip to the opposite ends of the caul assembly, and means for urging the pad and the strip against the abrasive belt.

4. A sanding and polishing machine comprising a frame, a pair of pulleys mounted for rotation on the frame, an abrasive belt extending over the pulleys, a work supporting table on said frame between said pulleys, a pad on the side of the belt opposite the table, a caul assembly mounted on the frame, said caul assembly having a pair of flanges extending along and overlapping the opposite sides of the pad, a first pair of endless belts mounted on opposite sides of the caul assembly, a second pair of endless belts mounted on the opposite sides of the caul, each of said endless belts having a run extending between said pad and said overlapping flange and having a length which is relatively thick and a length which is relatively thin, said thick and thin lengths being joined end-to-end and the junction in one of each pair of endless belts being in lateral alignment with the junction in one belt of the other pair of belts, means for moving the pairs of belts, and means for urging the pad against the abrasive belt, whereby the effective length of the pad is adjusted by the endless belts.

5. A sanding and polishing machine comprising a frame, a pair of pulleys mounted for rotation on the frame, an abrasive belt extending over the pulleys, a work supporting table on said frame between the pulleys, a pad on the side of the abrasive belt opposite the table, a caul assembly mounted on the frame, said caul assembly having a pair of flanges extending along and overlapping the opposite sides of the pad, a first pair of endless belts mounted on opposite sides of the caul assembly, a second pair of endless belts mounted on the opposite sides of the caul assembly, each of said endless belts having a run extending between said pad and said overlapping flanges and having a length which is relatively thick and a length which is relatively thin, said thick and thin lengths being joined end-to-end and the junction of each pair of endless belts being in lateral alignment, means for independently moving the pairs of endless belts, means for indicating the positions of said junctions, and means for urging the pad against the abrasive belt, whereby the elfective length of the pad is adjusted by the endless belts.

6. A sanding and polishing machine comprising a frame, a pair of pulleys mounted for rotation on the frame, an abrasive belt extending over the pulleys, a work supporting table on said frame'between said pulleys, a pad on the side of the belt opposite the table, a caul assembly mounted on the frame, said caul assembly having flanges extending along opposite sides thereof, a flexible sheet extending between and overlapping said flanges, said pad being secured to said sheet, said caul assembly having a backing plate extending along the sheet, an inflatable bag between the sheet and the plate, means for inflating the bag, a first pair of endless belts mounted on opposite sides of the caul assembly, a second pair of endless belts mounted on the opposite sides of the caul assembly, each of said belts having a run extending between said sheet and said flange and having a length which is relatively thick and a length Which is relatively thin, said thick and thin lengths being joined end-to-end and the junction of one of each pair of endless belts being in lateral alignment with a junction of the endless belts of the other pair, and means for moving the pairs of endless belts.

7. A sanding and polishing machine as defined in claim 1 wherein said thick lengths of the endless belts are formed of roller chains and said thin lengths of chain are formed of a thin strip.

8. In a sanding machine having a frame and a pad adapted to bear upon an abrasive belt, a caul assembly having a pair of flanges extending along and overlapping the opposite sides of the pad, an endless belt mounted on each opposite side of the caul assembly, each of said endless belts having a run extending between said pad and said overlapping flange, said endless belts each having a length which is relatively thick and a length which is relatively thin, and means for urging the pad against the abrasive belt, whereby the thick lengths of the endless belts displace the pad away from the flanges and only the undisplaced portion of the pad urges the abrasive belt against the workpiece.

9. In a sanding machine having a frame and a pad adapted to bear upon an abrasive belt, a caul assembly mounted on the frame, said caul assembly having a pair of flanges extending along and overlapping the opposite sides of the pad, an endless belt mounted on each opposite side of the caul assembly, each of said endless belts having a run extending between said pad and said overlapping flanges, said endless belts each having means thereon for displacing the pad away from said flanges, a flexible strip extending along the pad adjacent the abrasive belt, means for securing the strip to the opposite ends of the caul assembly, and means for urging the pad and the strip against the abrasive belt.

10. A caul assembly for urging an abrasive belt against a workpiece comprising a backing plate, a pad, means for support-ing the pad on the backing plate, means for urging the pad away from the backing plate, track means extending along the opposite edges of the pad and overlapping the pad on the side opposite the backing plate, and strip means extending along the opposite edges of the pad between said track means and said pad, said strip means having thick portions and thin portions whereby the thick portions of the strip means displaces a portion of the pad toward the backing plate to adjust the effective length of the pad.

11. A caul assembly for urging an abrasive belt against a workpiece comprising a backing plate, a pad, means for supporting the pad on the backing plate, means for urging the pad away from the backing plate, track means extending along the opposite edges of the pad and overlapping the pad on the side opposite the backing plate, a pair of endless belts each having a run extending along opposite edges of the pad between the track means and the pad, each belt having a thick portion and a thin portion, the thick portion of each belt extending from an end of the pad toward the opposite end to the same extent, whereby the thick portion of the belts displace an end of the pad toward the backing plate to adjust the effective length of the pad.

12. A caul assembly for urging an abrasive belt against a workpiece comprising a backing plate, a pad, means for supporting the pad on the backing plate, means for urging the pad away from the backing plate, track means extending along the opposite edges of the pad and overlapping the pad on the side opposite the backing plate, a first pair of endless belts each having a run extending along opposite edges of the pad between the track means and the pad and having a thick portion and a thin port-ion, a second pair of endless belts each having a run extending along opposite edges of the pad between the track means and the pad and having a thick portion and a thin portion, the thick portion of said first pair of belts extending from one end of the pad and the thick portion of said second pair of belts extending from the opposite end of the pad, and means for selectively moving the belts relative to the pad whereby the effective length of the pad is adjusted.

13 A sanding and polishing machine comprising a frame, a pair of pulleys mounted for rotation on the frame, an abrasive belt extending over the pulleys, a work supporting table on said frame between said pulleys, a pad on the side of the abrasive belt opposite the table, means mounted on the frame and having a pair of flanges extending along and overlapping the opposite sides of the pad, a pair of endless belts, said endless belts having runs extending between said pad and said overlapping flanges, respectively, said endless belts each having a length which is relatively thick and a length which is relatively thin, and means for urging the pad against the abrasive belt, whereby the thick lengths of the endless belts displace the pad away from the flanges and only the undisplaced portion of the pad urges the abrasive belt against the workpiece.

14. A sanding and polishing machine as defined in claim 13 including switch means for activating said means for urging the pad against the abrasive belt in response to a workpiece being inserted between said belt and said table whereby the pad is moved against the abrasive belt when a workpiece is adjacent the belt.

References Cited UNITED STATES PATENTS 2,910,809 9/1959 Heesemann 51151 3,145,509 8/1964 Heesemann 51-141 3,221,448 12/ 1965 Heesemann 51-141 ROBERT C. RIORDON, Primary Examiner.

D. G. KELLY, Assistant Examiner. 

1. A SANDING AND POLISHING MACHINE COMPRISING A FRAME, A PAIR OF PULLEYS MOUNTED FOR ROTATION ON THE FRAME, AN ABRASIVE BELT EXTENDING OVER THE PULLEYS, A WORK SUPPORTING TABLE ON SAID FRAME BETWEEN SAID PULLEYS, A PAD ON THE SIDE OF THE ABRASIVE BELT OPPOSITE THE TABLE, A CAUL ASSEMBLY MOUNTED ON THE FRAME, SAID CAUL ASSEMBLY HAVING A PAIR OF FLANGES EXTENDING ALONG AND OVERLAPPING THE OPPOSITE SIDES OF THE PAD, AN ENDLESS BELT MOUNTED ON EACH OPPOSITE SIDE OF THE CAUL ASSEMBLY, EACH OF SAID ENDLESS BELTS HAVING A RUN EXTENDING BETWEEN SAID PAD AND SAID OVERLAPPING FLANGE, SAID ENDLESS BELTS EACH HAVING A LENGTH WHICH IS RELATIVELY THICK AND A LENGTH WHICH IS RELA- 